Titanium pigments



Patented June 29, 1937 HTED STATES TITANIUM PIGMENTS Reginald Hill Monk,Rosemere, Quebec, Canada, assignor to American Zinc, Lead and SmeltingCompany, St. Louis, Mo., a corporation of Maine No Drawing. ApplicationDecember 21, 1933, Serial No. 703,490

3 Claims.

This invention relates to titanium pigments and particularly to suchpigments as contain zinc and titanium in the titanate form and to aprocess of producing such pigments.

While pigments comprising various titanates have been heretoforeproposed, the present invention has for its object the production of animproved pigment, having high opacity and wearing properties whenemployed in paints for outdoor purposes, which is inert to acid vehiclesand in the preparation of which the reaction between the Zinc oxide andtitanium oxide is so controlled as to ensure substantial completeness ofthe reaction, leaving little, if any, of the zinc oxide in the pigmentin the uncombined state.

The oxide of titanium is prepared from a sulphate solution which hasbeen made from the ore or concentrate in the usual known way whichconsists in the adjustment of the sulphuric acid employed for thesolution of the ilmenite or titaniferous sands, that is, the acidconcentration should be adjusted to meet the requirements fixed by thesolubility of the ore used. When, for instance, ilmenite is the sourceof the titanium, acid 25 of ordinary commercial strength may beadvantageouslyused, but in thecaseof titaniferous sands the percentageof rutile contained determines the concentration of S04 in the solventemployed.

This S04 concentration may be secured by utiliza- 30 tion of highpercentage acid alone or by addition to commercial acid of a bisulphateof an alkaline earth metal. The sulphated mass obtained from thisreaction is dissolved in water at a temperature not higher than 60 to 70C. so that a solution containing about 200 grams per litre of combinedTiOz is obtained for purposes of hydrolysis.

This solution, containing about 200 grams per litre of T102, (assulphate) is added to a suspension of a reagent in water at about 80 C.to pro- 40 vide nuclei about which the hydrolyzed oxide may precipitate.For this purpose may be used silica gel or a suspension of hydrous zincoxide equivalent in either case to about 1 or 2% of the H02 present inthe solution. The precipitated TiOz is washed and sufiicient zinc ormagnesium oxide is added to convert the adsorbed sulphate ions into zincor magnesium sulphate. This soluble sulphate is then removed by washingand recovered for further uses.

To convert the pure oxide of titanium into the titanate of zinc it isimportant that there should be present a small percentage of colloidalzinc oxide or colloidal titanium oxide in order that a rapid andcomplete reaction may occur at a sufiiciently low temperature to producea satisfactory pigment.

If the chloride of the combining substance dissociates at the calciningtemperature (about 825-900 C.) then this salt will provide the colloidalparticle for the start of the reaction. In

the case of the titanate of zinc, as the chloride of zinc boils oifwithout dissociation the function of the salt must be supplied by someother means. Therefore, there is employed either a colloidal TiOz formedby the addition of hydrochloric acid or nitric acid to the washed pulpor a hydrous zinc oxide prepared in some well-known manner and added tothe titanium dioxide and zinc oxide which are mixed together in theircorrect proportion (approx. 82 parts ZnO and 80 parts TiOz) to form azinc titanate.

Sometimes a combination of the two methods is desirable, the essentialpoint being that a complete conversion should take place. In any eventthe product should contain less than 5% uncombined zinc oxide.

The titanate so produced is superior to any mixture of zinc oxide andtitanium oxide while it retains the useful and desirable qualities ofsuch a mixture. It does not thicken in the usual vehicles and does notchalk or disintegrate upon exposure to the atmosphere when used as apaint in suitable vehicles.

What I claim is:

1. A method of producing a titanium pigment which comprises adding tohydrous zinc oxide in suspension a sulphate solution of titanium oxide,bringing the solution to a temperature of about 80 C., washing thehydrolyzed TiOz, neutralizing the adsorbed S03 with magnesium oxide,removing the magnesium sulphate so formed, adding to the pulp withstirring a small percentage of an acid capable of forming colloidal TiOzto act as a catalyst in the subsequent reaction, mixing with molecularproportions of zinc oxide and calcining the mass to produce zinctitanate.

2. A method of producing a titanium pigment which comprises adding tohydrous zinc oxide in suspension a sulphate solution of titanium oxide,bringing the solution to a temperature of about 80 C., washing thehydrolyzed TiOz, neutralizing the adsorbed S03 with zinc oxide, removingthe zinc sulphate so formed, adding hydrous zinc oxide to the pulp withstirring, mixing with molecular proportions of zinc oxide and calciningthe mass to produce zinc titanate.

3. A method of producing a titanium pigment Which comprises adding tohydrous zinc oxide in suspension at sulphate solution of titanium oxide,bringing the solution to a temperature of about 80 C., washing thehydrolyzed 'IiOz, neutralizing the adsorbed S03 with zinc oxide,removing the zinc sulphate so formed, adding to the pulp with stirring asmall percentage of an acid capable of forming colloidal TiOz to act asa catalyst in the subsequent reaction, mixing with molecular proportionsof zinc oxide and calcining the mass to produce zinc titanate.

REGINALD HILL MONK.

